The present invention relates to an electric motor-driven chain saw braking/locking apparatus in which a cutting chain is wound around and supported by a forwardly projecting guide bar provided on a housing carrying an electric motor therein, the chain being driven by the electric motor.
A chain saw manufacturer is under an obligation to provide a braking apparatus for stopping the driving of a cutting chain to prevent phenomena such as the chain guide bar being violently kicked back upwardly due to suddenly increased cutting resistance of the cutting chain (the kickback phenomenon) or the operator's hand sliding off the front handle and coming into contact with the cutting chain.
Conventionally, a hand guard is used as a braking apparatus for such a chain saw. The conventional hand guard is arranged such that a braking belt wound around the outer periphery of a clutch drum is tensed by swinging the hand guard forwardly to thereby apply a braking force to an output shaft so as to stop the drive for the cutting chain. This arrangement is disadvantageous in that the transmission section from the hand guard to the braking mechanism is indirect and complicated so that, due to an accompanying long transmission time between members, there is a delay in braking. Moreover, the cutting chain cannot be stopped rapidly because the braking mechanism is arranged such that the motor is forcibly stopped in its energized state by the braking force.